Exosome is a nano-sized vesicle naturally generated in a cell, and contains protein and genetic information to thus deliver diverse signals including the genetic information from the cell to other cells, thereby being involved in development, proliferation, differentiation, immune-modulation, angiogenesis, or progression of different diseases. The exosome as a bio-nanovesicle may avoid immune response and have excellent human-compatibility, and other advantages such as drug loading ability, target delivery effect to specific cells, stability in blood, etc., and therefore, recently drawing a great deal of attention as a drug delivery system.
Conventional liposome-based nanodrug delivery systems are employed in clinical applications. However, some technical limitations such as limited drug delivery efficiency to a target and a problem in releasing desired drug on a lesion site have been exposed. Accordingly, when the exosome is administered to a human body for purpose of playing a role of the drug delivery system, a method for assaying in vivo distribution of the exosome and whether the exosome is reliably delivered to a target organ may be required.
A variety of labeling techniques for image tracer of existing substances of biological origins (‘bio-derived’) or nano-substances have been proposed. However, in a case of exosome, in aspects of requirement for a labeling technique under physiological and environmental conditions in order to preserve characteristics of the exosome as a bio-derived substance, in addition, procedures and stability for regaining labeled exosome after labeling, it is difficult to label the exosome according to any typical method.
Korean Patent Laid-Open Publication No. 2013-0127276 discloses a method of analyzing exosomes using fluorescent material-labeled exosome, which includes binding the fluorescent material-labeled exosome to a solid support to analyze the exosomes. However, due to high background as a problem of fluorescent image itself, there is a limit to trace fluorescence-based exosome in a living animal.
Accordingly, it is necessary to develop a novel technique that can easily observe in vivo distribution of the exosome and determine whether the exosome moves toward a target organ and/or target disease through a nuclear medical image even in levels of human as well as small animals, due to the exosome is labeled with a material capable of replacing the fluorescent substance.